The question is incomplete, the complete question is;
Researchers investigated the influence of environmental pH on the activity of peroxidase, an enzyme that catalyzes the conversion of hydrogen peroxide to water and oxygen gas. In an experiment, the researchers added a hydrogen peroxide solution containing guaiacol to several identical test tubes and adjusted the solution in each test tube to a different pH. The researchers included the guaiacol because it caused the solutions to change color as the reactions proceeded, which the researchers relied on for measuring reaction rates. Finally, the researchers added the same amount of peroxidase to each test tube and measured the rate of each reaction at 23°C. The results of the experiment are represented in Figure 1.
Figure 1. The effect of pH on peroxidase activity
Which of the following actions will provide a negative control for the investigation?
A
Repeating the experiment at 25°C
B
Repeating the experiment using twice the amount of hydrogen peroxide
C
Repeating the experiment using twice the amount of peroxidase
D
Repeating the experiment using heat-denatured peroxidase
Answer:
D
Repeating the experiment using heat-denatured peroxidase
Explanation:
A Negative control is a situation in which a particular reagent added to an experimental set up just as all the other samples is not expected to effect any change in the responding variable.
In this case the independent variable is the pH of the solution while the responding variable is the activity of peroxidase enzyme.
A denatured enzyme is not expected to have any effect on the responding variable. Hence, this is a negative control.
